Electromagnetic power device.



A. K. T. SMITH & P. GOOD.

ELECTROMAGNETIC POWER DEVICE. APPLICATION FILED 11.29, 1911.

1,123,411. Patented Jan.5, 1915.

UNITED STATES.

PATENT OFFICE.

anrnn'n xnm'ilu. rounmm smrn AND rnnor soon, or LONDON, ENGLAND.

ELECTROMAGNETIC rowan DEVICE,

Specification of Letters Patent.

Patented Jan. 5, 1915.

Application filed April 29, 1911. Serial No. 624,212.

To all whom it may concern:

Be it known that we, ALFRED KnnoAn .Toomum SMITH and 'PnRoY GO0D,'.S11b]eCtS of they King of Great Britain, residing at London; S. England, have invented cer- This invention relates to electromagnetic powerdevices. g

The chief object of the invention is to provide an electromagnetic power device, giving a reciprocatory movement of long range and preferably exerting asubstantially uniform pull throughout the whole of its movement.

The electromagnetic power devices according to this invention are especially applicable for operating railway points or railway signal devices, brakes, stamp mills, and

like apparatus but their application is hot restricted thereto.

" According to this invention the electromagnetic power device comprises a central core with a limb or limbs or other membersof magnetic material arranged along its side or sides or surrounding it, and a reciprocator 1n the form of a coil or coils movable on the core, sa d reciprocator being of less .length than the air-gap inwhich it moves, and) the air-gap which surrounds the reciprocator increasing gradually toward the free endof the core, there beuig suitable magnetizing windings for the .core

or the core being permanently magnetized.

The invention will be more fully understood from the following description taken in connection with the accompanying drawingsin which:

Figure -l 1s a diagrammatic .view of one form ofelectromagnetic power device constructed according to this invention. Fig.

'2 isa perspective view of another form of device". Figs. 3, 4, 5, 6 and 7 are respectively diagrammatic viewsof other forms of the device. Fig. 8 is a sectional elevation of a deviceconstructed according to this'inven- .tioni. such as might befusedin practice for operating railway points or signals. Fig. 9

is a section of the device shown in Fig. 8,

taken on the line 00-41: in Fig. 8, looking in the direction of the arrows w, and'Figs. 10 and 11 are elevations on a reduced scale of the device :shown in Fig. 8-, looking in the direction of the arrow 3 in Fig. 8 and showing along its length on opposite sides of it,

and a magnetizing winding B is fixed at the position shown on-the central core A.

The central core A, the limbs A and the magnetizing winding B together form the stator. A reciprocator coil C, is movable on the central core A.

The coils of the stator and reciprocator are supplied with current from the same or different sources. If they are supplied from the same source they may be connected in series or parallel. The reciprocator is caused to move by altering the degree of energization on one or both of the wind ings. The reciprocator may be moved elecltromagnetically in both directions or it may be moved electromagnetically in' one direction, and by gravity, or a spring in the other direction. Ifthestator and reciprocator windings are supplied with direct current, then, on changing the direction of flow of the current'in either one of the coils, the reciprocator coil tends to move in the direction opposite to that tov which it has previously tended to move.. Similar efiects are obtained'with alternating current bv changing the'relative direction of the flow of the current in the reciprocator and magnetizing coils.- n

, The reciprocator. coil tends? to move on the central core so as to alter the magnetic flux passing through it.- *For any position :of the reciprocator coil on the central core the force will va tion of magnetic ux along the central core .and between l the latter and the limbs on each side of it. In-order to get a substantially uniform pull along the whole length of movement-of the. reciprocator coil it is according -'to the varia- I necessary that-lathe air-gap should increase toward the free ends of the central core and limbs. Such an arrangement is diagram-' matically illustrated in Fig. 1. v In order to provide thisuniform pull when a uniform current is flowing, it is necessaryto provide a uniform magnetic field in the air gap in the reciprocating coil. When current is sent through the reciprocating coil the magnetic reaction produced tends to make the strength of the magnetic field in the air gap, near the closed end of the core weaker and tends to strengthen it near the free end. In order to correct for this we increase the reluctance of the niagnetic circuit at the free end of the core-and by suitably proportioning this reluctance-we are able to obtain substantially the uniform field necessary to produce the uniform pull.

In the construction illustrated in Fig. 5 (hereinafter described), the above principle applies but the maximum reluctance in this core is required at the center which is the point at the greatest distance from either stator coil and is the portion which magnctically corresponds with the free end in the above case. M Referring to Fig. 2, acentral core A is fixed to theclosed end of a hollow conical -member A the otherend of this member A being open. The magnetizing coil B is fixed on the central core A? and a reciproca tor. coil C is movable'on the core A The operation of the device is exactly simil'arto that described in connection with Fig. 1.

In Fig. 3, a device similar to that shown in Fig. 2, is illustrated, the stator and reciprocator coils being of such form that the latter can more over the former. This obviously gives a-greater range of movement than in a construction where the reciprocator coil can only move up to thestator coil.

lVhen employing a device according to this invention for such an' operation as movrelatively small force vafter the signal has been brought to rest in one position. For this reason a smaller current may be employed for holdingon purposes such as just referred to. To further decrease the amount of current consumed the reciprocator coil may be provided withfa magnetic armature which comes close to' orengages the free ends of the central core and the limb or limbs or surrounding member. This is illustrated diagrammatically in Fig. 4, where the reciprocator coil C has attached to it an armature D, by means of rods D- WVhen the reciprocator coil moves as close as possible up to the stator coil B the armature D, bridges the free ends of the central core A, and the limbs A. To automatically diminish the current taken by the apparatus, an arrangement for automatically switching in a resistance. in the circuit is provided. The resistance E. is arranged in the circuit of the stator coil B and reciprocator coil C which are shown connected in series, F representing the battery, andG the operating key. The switch arm "H is pivoted at H and normally is held by a spring H in engagement with. a contact so as to mg a signal it is only necessary. to exert a form A".

short circuit the resistance E. As the reciprocator coil C moves up to the stator coil B a projection D on the armature D engages the switch arm II, so as to throw the resistance E into the circuit of the stator and reciprocator coils, thereby diminishing the current taken by them. v Referring to Fig. 5, a central core A is arranged with limbs or members A? connected to both of its ends. Two stator coils B are arranged at the two ends of the central core A and the reciprocator coil C is movable between them. The stator and reciprocator coils can be so connected to sources of electric current that'the reciprocator coil C is caused to move in either one or the other direction along the central core'A*. In this form of our device the core tapers inwardly from both ends, toward the center as shown so as to have the air-gap wider at the middle thanat the ends.

In Fig. 6, we have shown a modification of the device shown in Fig. 5, and in which the outer member A tapers inwardly from .the center to both ends thisconstruction having the Fig. 5.

In the modification shown in Fig. 7, a central core A is provided with two members A arranged beside it but not connected to it by magnetic material. A stator winding B is arranged at the center of the core A and two reciprocator coils C are arranged to move'on the core A. The stator and reciprocator windings may be supplied with current so that the reciprccator coils move in relatively the same or opposite directions at the same time. lVhen the coils move in relatively opposite directions at the same time thederice may be used where it is desirable or necessary to obtain such movement in the device to be. operated.

Referring to Figs. 8, 9, 10 and 11, a device constructed according to this invention is shown such as might be used in practice for operating railway points or signals. Its general form is similar to that described above in connection with Fig. 2. It comprises a central cylindrical core A surrounded by a member of substantially cylindrical At the base of the central core A there is a circularflange or disk A which screws into the cylindrical member A as shown. The device is bolted to any suitable base. The fixed coil B is arranged as shown, around the central core A A reciprocator coil C is provided which can move on the central core A Current from the source of supply is led to terminals J on the outside of the member A The terminals J are protected by a cover J. In Fig. 8, only one terminal is shown, the other one being directly behind it. Two leads B B connect the two terminals J respectively same effect as that shown in to the stator coil B.

into the upper flange of the bobbin. The

leads K are flexible and are connected to the two terminals J respectively so that the stator and reciprocator coils are in parallel. The tubes L at their upper ends screw into a plate M. Screwed into the plate M are two pillars M, to which is-attached a plate M by nuts. The plate M has screwed into it a draw-hook N. The draw-hook N holds in position a casing O and between the top of the casing and the plate M is a conical block of wood O- The plate M is provided with a hoie at its center through which passes a rod M The rod M at its lower end screws into an armature P. A spiral spring M surrounds part of the rod M and is retained between the plate M and the armature P. The upper end of the rod M is provided with a flange or washer M held in position bv a nut M. A spiral spring M is held in position by the flange M and the plate M. The springs M and M, actin in conjunction with the rod M form a exible connection between the plate M and the armature P and also act as bufi'er springs between the reciprocator and the armature P. The armature P has portions cut away at P" to regulate the force of attraction with which it is held on to the core A and member A". It is also provided wtih holes P through which the tubes L pass, these holes being of suflicient diameter to permit of the armature P having a tipping movement relatively to the plate M. With this construction it is possible for the armature to takevup a true position with relation to the ends of the cores A and member A", even if the plate M is tipped, for example by a side pull on the draw-hook N. The coils on the stator and reciprocator may be completely inclosed by, for example, brass so as to be damp proof. The device may be filledwith oil to produce a dash-pot action on the reciprocator. The gap between the central core A and the member A gradually increases toward the free end of the core A for the purpose.of obtaining ,uniformity of pull, as described in connection with Fig. 2.

With the construction described above the reciprocating coil or coils can move close up to the stator so that practically the whole of the lines of force set up by the stator coil pass through the reciprocating coils, therey enabling the apparatus to be constructed with a very high efliciency.

We claim 1. In an electromagnetic power device, the combination with a central, normally magnetized, core, of a reciprocator consisting of a coil, formed without magnetic ma-' terial, surrounding the core and movable thereon and an external member composed of magnetic material, magnetically connected, at one end only, to the core and gradually flaring outwardly from the core and said core being magnetized independently of any magnetism produced by the reciprocator.

2. In an electro-magnetic power device,

the combination with a central, normally magnetized, core, of a reciprocator consisting of-a coil formed without magnetic material and surrounding the core member and an external member composed of magnetic material, said external member being magnetically connected to the core member, at one end only, and extending outside the said reciprocator, one of said members being so formed as to-produce an air-gap increasing gradually from a point adjacent the point of connection of said member, and said core being magnetized independently of any magnetism produced by the reciprocator. 3. In an electro-magnetic power device, the combination with a central normally magnetized core, and a reciprocator consisting of a coil formed without magnetic material surrounding the core and movable thereon, of a hollow conical member magnetically connected, at one end only, to one end of the core and open at its'other end and providing an ually in size toward the open end of said member, and said core being magnetized independently of any magnetism produced by the reciprocator.

In testimony whereof we affix our signature in presence of two witnesses.

ALFRED KENDAL TOULMIN SMITH. PERCY GOOD. Witnesses:

EUSTACE H. BARKER, WILLIAM E. WYATT.

air-gap, increasing grad-- 

